1. Field of the Invention
The present invention relates generally to a system for providing wireless messaging, and specifically to a system for providing bidirectional wireless electronic mail.
2. Description of the Prior Art
Short Message Services are provided by operators of wireless communication systems today who have digital service available. Short Message Services, or more simply put "SMS", are messages delivered by the wireless network to a digital phone. There are three major digital standards commonly deployed throughout the US today; Code Division Multiple Access ("CDMA"), Time Division Multiple Access ("TDMA"), and Global Systems for Mobile ("GSM").
Global Systems for Mobile ("GSM") is a specification that was written to provide a unified digital platform that all 12 countries of the European Community ("EC") could use from one country to the next with the same phone. Other countries outside of the EC have adopted GSM as their preferred system specification increasing the volume of systems worldwide. The first systems went commercial in 1993 in Europe, while the first commercial GSM system in the United States went commercial at the end of 1995.
GSM is similar to IS-54 TDMA (see below) in that it uses FDMA to separate RF carriers and TDMA to serve up to 8 users per channel. It was developed to provide a single European standard and to facilitate many new enhanced services and automatic roaming. Initially, GSM used the 900 Mhz band but has now added two compatible standards: DCS1800 at 1.8 Ghz and PCS1900 at 1.9 Ghz. TDMA (or D-AMPS) began life as a digital upgrade to the 800 Mhz AMPS network and is commonly referred to as IS-54. It employs the 30 kHz AMPS channel split into three timeslots with a separate control channel. The standard was upgraded to IS-136 to include an integrated digital control channel and interband operability to 1900 Mhz. CDMA was developed to provide further capacity enhancements over the TDMA standards. It uses Direct Sequence Code Division Multiple Access to differentiate users on the same 1.28 Mhz frequency band. CDMA systems are currently operating at 800 Mhz and 1900 MHz.
The US and other countries also decided that there was enough demand for wireless services in the marketplace to introduce more competitors into each market. The amount of new competitors has varied from country to country, but they have consistently used the higher frequency band in the 1900 MHz band. This new license area is generally known as Personal Communication Services ("PCS"), and six new licensed providers have been introduced in each market throughout the US. The two existing operators are generally referred to as "Cellular" operators and operate in the 800 MHz band throughout the US.